CRISPR editing check with BWA and SAMTOOLS v2

This tool supports both paired end fastq files (for example, xxx_R1_001.fastq.gz and xxx_R2_001.fastq.gz) and single end fastq files (please make sure they have suffix1 below).
Please run the 3 steps below to get the indexed bams from a list of fastq files.

Recommend using private browser windows to avoid troubles caused by cookies and caches (open from the menu at the topright corner)

No spaces are allowed in input file names!

Provide the suffix of your fastq files:

I. Choose reference file (a fasta file)

II. Choose demultiplexed fastq(.gz) files

III. Map reads and create bam files

After loading the template fasta file and all the fastq files, now we will use bwa and samtools to create indexed bam files for viewing in the software IGV.

min mapping quality when calling variants


This tool is a WebAssembly implementation of BWA and SAMTOOLS. It runs commands like this:

## map reads to the templates with bwa
bwa index <your-references.fa>
bwa mem <your-references.fa> <R1.fastq.gz> <R2.fastq.gz> > out.sam
## make sorted bam files with samtools
samtools sort out.sam > out.bam
samtools index out.bam
## I added editcall.c to bwa tool sets to call variants
bwa editcall -f your-reference.fa -o calledSNPs.txt out.sam

Visit the GitHub page for more details:

Enable SIMD for your browser

BWA needs SIMD for vector calculation. Please enable it in your web brower first (just need to do once).

  • chromium based browsers (Google Chrome and new Microsoft Edge): go to URL chrome://flags/, search WebAssembly SIMD support, and select “Enabled”; seems enabled by default since 2021.

  • Firefox: go to URL about:config, search javascript.options.wasm_simd, then choose true; seems enabled by default since 2022.

  • Other browers were not checked.


  • 2022-05-08: add editcall nim version to call indels and inversions from bwa mem sam file.
  • 2022-05-30: add editcall c version to call SNPs, indels and inversions from bwa mem sam file.
  • 2022-05-30: removed exactSNP results due to its wrong call of SNPs.
  • 2022-12-27: support single end reads now.
  • 2023-11-02: bwa-mem now put the reads with mapq=0 (multi-map) in the same chromosome as its mate if its mate has mapq > 0.


  • Thank the authors of bwa, samtools and Subread.
  • Thank Robert Aboukhalil for his development of aioli and biowasm. I successfully compiled bwa, samtools and Subread by learning the patch and compiling scripts from biowasm.